The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in the present disclosure and are not admitted to be prior art by inclusion in this section.
In 3GPP network, the physical uplink control channel (PUCCH) is used to transmit uplink control information (UCI) from a UE to a 3GPP eNodebB (eNB). An example of the UCI information is an acknowledgement signal in a hybrid-ARQ (HARQ) process. Typically, PUCCH resources are dynamically allocated to a mobile station based upon the lowest carrier control element (CCE) index of a signal transmitted on the PDCCH by the eNB using one or more CCEs. Because the PDCCH transmission is unique to a given UE, use of the CCE index would result in the UE being assigned a unique uplink resource on the PUCCH.
However, an ePDCCH using one or more enhanced carrier control elements (eCCEs) has recently been introduced to the 3GPP specifications. The uplink resource of the PUCCH may be based on the lowest eCCE index for one or more eCCEs used for a transmission on the ePDCCH. In certain instances the lowest CCE index and the lowest eCCE index may be the same. In these instances, an uplink resource allocated to a first UE using the lowest CCE index of the PDCCH may be the same as an uplink resource allocated to a second UE using the lowest eCCE index of the ePDCCH, resulting in a resource allocation collision.